Carburizing box



` Dec. 14, 1937.v A. M; MILLER CARBURIZING Box Filed sept. 11, 193e o. m Mw E. mwwm LC u M NJW@ Sw wn MS, aw a m. 1 l/ 2F Patented Dec. 14, 1937 UNITED STATES PATENT oFFlcE y oARBUaIzING Box Angus M, lMiller, Pleasant Ridge, Mich. `Amiliwtion september 11,1936, serial Ndiooao 1 claims. (ci. 263-49) My invention'relates /tocarburizing boxes and relates more particularly to carburizing boxes of a type having walls in the form of plates or sheets of heat resisting material. f

5 Inthe use of carburizing boxes, metal articles to be carburized are placed inthe boxes, together with any suitable carburizing agent such as bone dust. The boxes are commonly introduced into a heat treatingiurnace, with suitable covers, in trays,`and whenso introduced are subjected to the heat of/burning gases projected into the furl nace and which are usually directed against the sides and ends of the'box,'to cause heatto permeate the box, the contained articles, and carburizing agent. untilthe articlesare heated to a desired pre-determined temperature, whereupon the metal articlesabsorb carbon from the carburizing agent` Theeiect of the temperature which may reach 1 20 from 16oo to 1soo Fahrenheit is to add to the carbon content of the surface portions of the iron or steel articles. rAfter the carburizing operation, the boxes are thenwithdrawn from the furnace and cooled, and the accrued heat imposed upon the articlesbecomes` gradually dissipated. Consequently the boxes are subjected to extreme variations in4 temperature'and in former constructions, due to the expansion and contraction of the walls of such boxes, and more particularly the side walls, these walls commonly become peraged. Also in prior constructions there has been diiiiculty incurred, inl that some of the metal manently warped, fractured or otherwise damarticles placed in the box tobe'carburized become `heated to carburizing temperature more rapidly thanother articles diierently disposed in the box, and .the reverseV condition, that some of the articles are cooled more rapidly than other differently disposed articles, also commonly obtains, with the result that the articles are not uniformly carburized. Y

-It is therefore-an object of my invention to provide animproved carburizing box whereby all of the articles placed therein, and subjected tothe carburizing temperatures, are more uniformly subjected, and for more uniiorm'periods, to corresponding variations in temperature, both during theheating and cooling periods.` Another objectof my inventionis to provide an improved carburizing box, which will with-stand the temperature conditions incidental to the use of such a boxjunder the conditions of practice with minimum deterioration. Another object of my" invention is to provide a box which `will not onlyeiciently' with-stand the temperature conditions' of practice, but at the same time, will with-stand the hardmechanical usage imposed upon such a 'box in practice.

Another object of my invention is to provide a 5 carburizing box having lateral walls preferably continuous throughout their length, and which are so associated with the corners, as l to `provide what I terma full-il'oatingconstruction wherein said walls are not rigidly secured to the corners. 10

Another object of my invention is toprovide a carburizing box wherein the preceding objects may be achieved, and at the same time wherein the advantageous results arising out of a spaced double wall constructionmay also be `achieved.` `l5 Another object of my invention is to provide an improved carburizing `box having vsheet metal walls so formed and disposed relative to the cor-` ners, that thermal expansion and contraction and vmechanical usage will not unduly derange 20 the form of the walls, and will not cause the walls to deteriorate, and will not eiect breakage due to crystallization adjacent the corners which hold said Walls in position.

Other objects of the invention will be apparent 25 to those skilled in the art to which my invention appertains, from reference to theacccompanying drawing, and from the descriptive specification referring to said drawing, and which disclose a preferred embodiment of vmy invention. 30

Referring to the drawing:

Fig. 1 is atop plan view of a carburizing box which is an embodiment of my invention;

Fig. 2 Ais a side elevational `view of said box;

Fig. 3 is approximately a perspectiveview of 35 the corner construction illustrating the junction of corner `elements with the continuous side wall plates, a portion of the corner elements being illustrated in section;

Figs 4 and 5 are respectively horizontal sec- 40 tional'and vertical sectional views of a corner element, and the adjacent associated portions of the double side wall plates; l

` Fig.` 6 is a plan view of a. carburizing box cover;

Fig. 7 is a side elevational view thereof; 45 I Fig. 8 is a vertical sectional view taken on the line 8-8 of Fig. 6.

Referring now to the carburizing box illus- `trated in Figs. l, 2, 3, 4 and 5, the embodiment 50 ofthe carburizing box of my invention illustrated in saidfigures, is provided with a single pair of side Wall sheets or plates 3 and 4, which are bent into generally rectangular form with rounded corner portions 3' and 4 in which form they 55 are held by being fitted within oppositely extending arcuate slots 5 of the corner elements 2.

The lateral Wall portions 3 and 4 extend divergingly outwardly from preferably within the slots 5, and are most greatly relatively spaced intermediate the corners 2, and the spacing at said intermediate portion is maintained by a spacer element 6, which extends longitudinally of the box axis Aand intermediate the plates 3 and 4, being welded as by a laterally extending flange I preferably to the inner surface of the outer plate 4. Y

The plates 3 and 4 being each preferably in one piece, and each 4have their ends welded together as indicated at 8 for the inner wall plate, and at 9 for the outer wall plate.

The corner elements each comprise a pair of like relatively reversed parts I0 and II having oppositely disposed hook shaped fianges'l2.

The corner element parts I0 and II are welded together at their corresponding and abutting ends as shown at I3, preferably medially of the ends of the box. Each of said plates is provided with an arcuate intermediate portion 2 and an inwardly extending end flange I2 with a, reversely turned flange portion I2'. Said flange I2 and flange portion I2' are arcuately formed corresponding to the curved portion 2 of the corner element, and there is thereby provided an ar cuate slot 5 into which the inner and outer plates 3 and 4 may be loosely projected. The slot 5 at its ends I3 and I4 has divergcntly formed lateral walls to prevent localization of bending fatigue stresses at the point of emergence of said plates 3 and 4 from said slot 5.

The plates 3 and,4 are only loosely fitted in the corner elements 2 whereby the full-floating characteristic of the sheet metal walls is provided. The spacers 6 prevent more than a pre-determined relatively approaching movement of the Walls 3 and 4, but do not limit the relatively outward bowing of said walls under the influence of high temperatures.

In the use of the box of my invention, however, assuming that the box, perhaps with other boxes, is placed in a suitable tray and provided with any suitable top closure, and introduced into the carburizing furnace, the side walls of the boxes are subjected to the heat of burning gases or other source ofv heat provided in the furnace for a pre-determined length of time, and at the same time heat is communicated through the bottom tray and top cover to the carburizing material and articles to be carburized in the box.

In single walled boxes of the prior art, it hasbeen' found that heat commonly penetrates the side walls and is communicated to the articles disposed most nearly adjacent to said side walls more rapidly than to articles placed nearer the center of the box, and also that such more nearly adjacent articles are cooled more rapidly than the more centrally disposed articles. This results in a difference in carburizing results imposed upon the said differently disposed articles in the box.

Another difficulty which has been prevalent with single walled boxes is that heat is transmitted through the lateral walls more rapidlyl than from the tops and bottom and with a resultant difference in carburizing results with respect to some of the lateral surfaces of articles positioned relative to other surfaces which may be faced towards the top or bottom.

The carburizing agent being a quite eflicient form of heat insulation material, and being so placed as'to surround the articles in`the box, adds to the difliculties such as those above mentioned, which have been previously prevalent.

In my improved double wall construction, the air space between the outer wall and inner wall elements, retards the flow of heat communicated to the outer wall element, to the articles placed within the box.

In my improved box having the relative dimensions as illustrated in the drawing, it is found that heat transmitted to the articles disposed over the major portion of the interior of the box, from the top and bottom of tray and cover elements, arrives at the articles within the box, at about the same time as the heat transmitted through the double walls, and communicated laterally to such articles.

Conversely after the carburizing operation, and upon cooling, heat is dissipated in all tlirections from the articles at approximately the same rate, or in any event, at a more uniform rate in all directions than has been previously attained in boxes of this general character.

Now referring to Figs. 6, 7 and 8. I have illustrated therein a form of top or bottom cover element, which I prefer to use with the box of my invention, although obviously, said box is not limited to any particular form of cover or tray, and may be employed in connection with any well known form of cover or tray.

The cover of said figures which may also be used with other forms of boxes comprises a substantially rectangular plate I5, loosely held between parallel flanges IS and I 1, which extend inwardly from a relatively short substantially rectangular tubular frame I8.

'Ihe frame I8 with the inwardly extending flanges I6 and I1 is preferably made of two separate castings I9 and 20, welded together at preferably diametrically opposite points 2| and 22, the line of weld extending preferably parallel to the axis of the frame.

Between the portion of the plate I5 which extends between the flanges I6 and I'I, and the frame element I8 excluding said flanges, sumcient clearance is provided, so that the plate relative to said frame is relatively oatlng inthe slot provided by said flange, in both lateral and vertical directions within predetermined limits.

In Fig. 8 the position of a carburizing box 20 with respect to which the cover oi' Fig. 8 may be employed is shown.

Ordinarily the box of -my invention is used in connection with trays of the ordinary types on which the boxes are placed, but under special conditions, a cover element such as illustrated in the foregoing figures may be employed as a tray, and when so employed the plate I5 should preferably be made heavier.

Having thus described my invention in a preferred embodiment, and with a preferred form of top and bottom, I am aware that numerous and extensive departures may be made from the invention herein illustrated and described, but Without departing from the spirit of my invention, I claim:

1. In a carburizing box, a pair of one-piece relatively telescoped spaced sheet metal wall elements each bent to substantially closed rectangular form, said box comprising said sheet metal elements and corner elements, said corner elements loosely embracing the top and bottom. edge portions of suitably bended corner portions of said wall elements.

ments and corner elements, said corner elements loosely embracing the top and bottom edge portions oi suitably bended corner portions of said wall elements, said wall elements being of substantially bowed. form intermediate each pair of adjacent corner elements, whereby they are separated from eachother providing an air space l betweenv said elements. A

3. `In a carburizing box, a pair ofone-piece relatively telescoped sheet metal wall elements each bent to` substantially closed rectangular form, said box comprising said sheet metal elements 1and corner elements, said corner elements `loosely embracing the top and bottom edge portions of suitably bended corner portions of said wall elements, said wall elements being of substantially bowed form `intermediate each pair oi adjacent corner elements, whereby they are separated from each other providing an air space between said elements, and spacer means interposed between element bent to generally rectangular form, and corner elements. said corner elements having flanged ends and provided with relatively confronting slots on the ange of each end, said wall elements being loosely received within beth of the confronting slots of each corner element.

6. In a. carbuiizing box, a pair of one-piece relatively vtelescoped sheet metal wall elements each bent to substantially tubular rectangular form and with their abutting edges secured together, a corner element secured to said wall ele ments at the corners thereof,said corner elements embracing the top and bottom edges of the corner portions of saidwall elements by 'slots of said corner elements, thesize and form of said slots being `such as to ensure a loose clamping t between said wall elements and said corner elements, said wall elements extending divergingly fron each of said corner elements and relatively spaced over at least the major portion of their `lengths between corner portions.

7. In a carburizing box, a pair of one-piece each bent to substantially tubular rectangular said innerand outer` Wall `elements intermediate\\ form and with their abutting edges secured tosaid corners, to ensure a predetermined separation between said wall elements adjacent said spacer means.

4. A carburizing box comprising a pair of substantially continuous one-piece substantially tubular sheet'metal spaced walls, each wall bent to i generally rectangular form, and corner elements, said corner elements having `flanged ends and provided with relatively confronting slots on the iiange of each end, said Wall elements being received within both of the confronting slots of` each corner element.

5. A carburizing box comprising a pair of substantially continuous one-piece substantially tubular spaced sheet metal wail elements, each wall .gether, a corner element secured to said wall ele- `their lengths between corner portions, and spacer means to ensure at least a predetermined spacing of saldfwallelements intermediate said corner elements. K

ANGUS M. MILLER. 

